Investigators who conduct studies designed to assess familial transmission of a vulnerability or resistance to drug abuse often interpret some of their findings as evidence of a genetic determinant. Families not only share genes but they also share an environment. Parents influence their children through modeling and the establishment of acceptable norms of behavior. This may include the formation of expectations about the effects of drugs. This study is designed to determine whether instructions can alter the mood effects of test drugs. The study consists of two experiments. In both, participants are trained to discriminate between 75 mg tripelennamine and placebo. In the first experiment, they are told that the capsules they receive might be a sedative, stimulant or placebo but that one of them is more sedative-like than the other. They are also informed that their discrimination will occasionally be tested, mostly with sedatives. These instructions are designed to bias the subject to report sedative-like effects. The second experiment is identical except that the instructions are designed to bias the subject to report stimulant-like effects. During both experiments, 4 drugs/doses will be tested: 2.5 and 5 mg diazepam and 5 and 10 mg d-amphetamine. It is expected that during the first experiment these low doses of diazepam, which previous studies have shown do not have robust sedative-like effects, will be identified as tripelennamine and clearly labeled as a sedative. Likewise, the malleable effects of amphetamine seen in previous studies should result in most subjects identifying at least the 5 mg dose as sedative-like. In contrast during the second experiment, it is more likely that a test drug will be identified as placebo and labeled as a stimulant. To date, 7 participants have completed both experiments with an additional two completing the stimulant experiment only and an additional one who completed the sedative experiment only. Preliminary analyses of the data indicate that discrimination and drug labeling results are consistent with the hypotheses.